An antenna is one of most important front-end passive components of a communications device. The antenna has a very important role in performance of a communications product. An array antenna basically includes two parts: a feeding network and an antenna element array. It is generally required that signals output by the feeding network to all antenna elements are equal in amplitude and identical in phase with a small feeder loss, and a distance between two antenna elements is a half of an operating wavelength with high radiation efficiency.
A feeding network of an existing array antenna may be generally implemented in several manners, such as using a microstrip, a waveguide, and a substrate-integrated waveguide. It is easy for a microstrip feeding network to meet the requirement for equal amplitude and an identical phase by using a parallel feeding structure design, but a microstrip line has a large loss at a high frequency and has poor performance. The waveguide has a minimum transmission loss, but generally only a serial feeding manner can be used due to a large waveguide size; therefore, the requirement for equal amplitude and an identical phase can be met only within a narrow frequency range. If a parallel feeding manner is used, due to a waveguide width limitation, it is not easy to meet the requirement that a distance between antenna elements is a half of an operating wavelength. The substrate-integrated waveguide has a small loss and is easier to be processed and integrated than the waveguide, but the substrate-integrated waveguide has a same problem as the waveguide, that is, the requirement that a distance between antenna elements is a half of an operating wavelength cannot be met due to the width limitation.
Therefore, the array antenna in the prior art has disadvantages of a large loss at a high frequency, poor performance, and narrow bandwidth.